MohidWiki - User contributions [en]

Coupling Water-Atmosphere User Manual

2008-08-18T13:12:35Z

193.136.129.1: /* References */

== Overview ==
This user manual intends to help MOHID users to construct properties in the atmospheric and interface water-air compartments, in a way that his modeling needs are fulfilled.
The document tries to answer to three main processes in what atmosphere takes part: i) wind forcing; ii) heat fluxes between air and water; iii) mass fluxes between air and water.

Momentum fluxes, Oxygen and Carbon fluxes are not yet considered in this user manual.

Heat fluxes between air and water command water warming and cooling processes and thermal stratification formation. Wind can play an important role on surface stress and on mixture depth control, destroying stratification. Thus, when thermal stratification in natural systems occurs, and 3D model is used, both processes should be simulated.

Mass fluxes can be important if level variations due to precipitation and evaporation or water abstraction are important.

== Inputs Required ==

=== Wind Forcing ===
If one wants to simulate wind stress on water interface and account its role in hydrodynamic circulation some keywords and properties must be added to data files.

==== Hydrodynamic Data File ====
* '''Keyword “WIND”''' value has to be equal 1 (one): Ex: '''WIND : 1'''.

==== InterfaceWaterAir Data File ====
* '''Property “wind stress X”''' and '''Property “wind stress Y”''' must be defined. These properties can be a constant value, entered as timeserie or computed by the model (REMAIN_CONSTANT : 0).

==== Atmosphere Data File ====
* If Properties “wind stress X” and “wind stress Y” in InterfaceWaterAir data file are to be computed, then '''Property “wind velocity X”''' and '''Property “wind velocity Y”''' must occur in atmosphere data file. These properties can be a constant value, entered as timeserie or computed by the model (REMAIN_CONSTANT : 0).
* If Property “wind velocity X” and Property “wind velocity Y” are to be computed, this is done with wind modulus and wind angle. Then '''Property “wind modulus”''' and '''Property “wind angle”''' must occur in atmosphere data file. These properties can be a constant value or entered as timeserie.

=== Heat Fluxes ===
In MOHID heat fluxes in water column are computed with:

i) a heat source: solar radiation that enters through the water surface (surface radiation - see description in Module InterfaceWaterAir) suffering a decay with depth (light extinction).

ii) a boundary condition for surface: non solar flux (see description in Module InterfaceWaterAir)

iii) a boundary condition for bottom: no flux, all radiation reaching the bottom is transformed in heat

If one wants to simulate heat fluxes on water interface and account its role in water temperature some keywords and properties must be added to data files.
The next image ilustrates heat fluxes in MOHID and atmosphere, interface water-air and water properties that are called to compute them.
[[Image:FluxosCalor_MOHID.png|thumb|center|600px|Water-Atmosphere heat fluxes and related properties in MOHID]]

==== WaterProperties Data File ====
* '''Property “temperature”''' must be defined because it is the state variable in water column affected by heat fluxes. Inside this property, block '''keyword “SURFACE_FLUXES”''' value has to be equal 1 (one) so that water-air fluxes can be considered.

==== InterfaceWaterAir Data File ====
* '''Property “surface radiation”''' must be defined in InterfaceWaterAir data file. This property accounts for solar flux trough the water surface and can be a constant value, entered as timeserie or computed by the model (REMAIN_CONSTANT : 0).
* '''Property “non solar flux”''' must be defined in InterfaceWaterAir data file. This property accounts for non solar flux (latent heat, sensible heat, etc) trough the water surface and can be a constant value, entered as timeserie or computed by the model (REMAIN_CONSTANT : 0).
**If Property “non solar flux” has to be computed than this is a balance between latent heat, sensible heat and long wave radiation trough the water surface. Thus '''Property “latent heat”''', '''Property “sensible heat”''' and '''Property “net long wave radiation”''' must be defined in InterfaceWaterAir data file. These properties can be a constant value, entered as timeserie or computed by the model (REMAIN_CONSTANT : 0).
**'''Remark''': latent heat and sensible heat depend on water temperature so they should be computed by the model. Net long wave radiation is a balance between downward long wave radiation (emission from the atmosphere) and upward long wave radiation (emission from water) and should be computed by the model.
***If Property “net long wave radiation” has to be computed than '''Property "downward long wave radiation"''' and '''Property "upward long wave radiation"''' must be defined in InterfaceWaterAir data file. These properties can be a constant value, entered as timeserie or computed by the model (REMAIN_CONSTANT : 0).
***'''Remark''': upward long wave radiation depends on water temperature so it should be computed by the model.

==== Atmosphere Data File ====
* If Property “surface radiation” in InterfaceWaterAir is to be computed by the model, '''Property “solar radiation”''' must be defined in Atmosphere data file. This property can be a constant value, entered as timeserie or computed by the model (REMAIN_CONSTANT : 0). If this property is to be computed by the model, in Atmosphere data file '''keyword RADIATION_METHOD''' (global variable) must define if it is MOHID method (value 1 - by default) or CE-QUAL based (value 2). See Solar Radiation theory for more details.
**If Property “solar radiation” is to be computed also '''Property “cloud cover”''' is needed in Atmosphere data file. If Cloud Cover is computed, '''Keyword CLOUD_COVER_METHOD''' (global variable) must define if it is computed from sun hours (value 1), from radiation (value 3) or from random values (value 2 - by default).
**'''Remark''': Solar Radiation is a common property in INAG meteorological stations so, if available, data should be entered in timeserie format instead of computing with the model. Notice that if radiation is computed the model needs cloud cover and if cloud cover is computed (from radiation)it needs radiation.
* If Property “sensible heat” in InterfaceWaterAir is to be computed it is needed air temperature and wind velocity for the formulation . Thus, '''Property “air temperature”''' and '''Property “wind velocity X”''' and '''Property “wind velocity Y”''' must be defined in Atmosphere data file. These properties can be a constant value or entered as timeserie; wind velocity X and wind velocity Y can in addition be computed from Property “wind modulus” and Property “wind angle”, as stated previously (see 2.1.3). These last properties can be a constant value or entered as timeserie.
* If Property “latent heat” in InterfaceWaterAir is to be computed properties needed are the same as in Property “sensible heat” plus humidity. Thus, '''also Property “humidity”''' has to be added in Atmosphere data file. This property can be a constant value or entered as timeserie.
* If Property “downward long wave radiation” in InterfaceWaterAir is to be computed, then '''Property “air temperature”''' and '''Property “cloud cover”''' need to be defined in Atmosphere data file. These properties can be a constant value or entered as timeserie; cloud cover can in addition be computed by the model. If cloud cover is computed, '''Keyword CLOUD_COVER_METHOD''' (global variable) must define if it is computed from sun hours (value 1), from radiation (value 3) or from random values (value 2 - by default).

=== Mass Fluxes ===
Mass fluxes should be computed if level variations due to precipitation, evaporation or water abstraction are important.
Surface water flux is defined as the balance between Precipitation, Evaporation and Irrigation.

==== Hydrodynamic Data File ====
* '''Keyword SURFACEWATERFLUX''' value has to be 1 (one). Ex: '''SURFACEWATERFLUX : 1'''.

==== InterfaceWaterAir Data File ====
* '''Property “surface water flux”''' must be present in InterfaceWaterAir data file. This property can be a constant value, entered as timeserie or computed by the model.
**If Property “surface water flux” is to be computed by the model then the three properties needed for the balance can appear: Precipitation, Irrigation and Evaporation (this is not mandatory, properties that not appear, are not considered). Thus, '''Property “evaporation”''' can be defined. This property can be a constant value, entered as timeserie or can be computed by the model from latent heat. As so, if Property “evaporation” is to be computed by the model, also '''Property “latent heat”''' must be defined (see 2.2.2).

==== AtmosphereDataFile ====
*If Property “surface water flux” in InterfaceWaterAir data file is to be computed by the model then the three properties needed for the balance can appear: Precipitation, Irrigation and Evaporation (this is not mandatory, properties that not appear, are not considered). Thus, '''Property “precipitation”''' and '''Property “irrigation”''' can be defined. These two properties can be a constant value or entered as timeserie.

== Example Data Files ==

=== InterfaceWaterAir Data File ===
OUTPUT_TIME : 0. 86400

<begin_rugosity>
INITIALIZATION_METHOD : CONSTANT
DEFAULTVALUE : 0.0025
REMAIN_CONSTANT : 0
OUTPUT_HDF : 1
TIME_SERIE : 0
<end_rugosity>

<beginproperty>
NAME : wind stress X
UNITS : N/m2
DESCRIPTION : Calculated wind stress X
DEFAULTVALUE : 0
REMAIN_CONSTANT : 0
TYPE_ZUV : z
OUTPUT_HDF : 1
TIME_SERIE : 0
<endproperty>

<beginproperty>
NAME : wind stress Y
UNITS : N/m2
DESCRIPTION : Calculated wind stress Y
DEFAULTVALUE : 0
TYPE_ZUV : z
REMAIN_CONSTANT : 0
OUTPUT_HDF : 1
TIME_SERIE : 0
<endproperty>

<beginproperty>
NAME : latent heat
UNITS : W/m^2
DESCRIPTION : Calculated latent heat
FILE_IN_TIME : NONE
REMAIN_CONSTANT : 0
DEFAULTVALUE : 0.
TIME_SERIE : 0
OUTPUT_HDF : 1
<endproperty>

<beginproperty>
NAME : sensible heat
UNITS : W/m^2
DESCRIPTION : Calculated sensible heat
FILE_IN_TIME : NONE
REMAIN_CONSTANT : 0
DEFAULTVALUE : 0.
TIME_SERIE : 0
OUTPUT_HDF : 1
<endproperty>

<beginproperty>
NAME : surface radiation
UNITS : W/m^2
DESCRIPTION : Calculated infrared radiation
ALBEDO : 0.05
FILE_IN_TIME : NONE
REMAIN_CONSTANT : 0
DEFAULTVALUE : 0.
TIME_SERIE : 0
OUTPUT_HDF : 1
<endproperty>

<beginproperty>
NAME : net long wave radiation
UNITS : W/m^2
DESCRIPTION : Calculated net long wave radiation
FILE_IN_TIME : NONE
REMAIN_CONSTANT : 0
DEFAULTVALUE : 0.
TIME_SERIE : 0
OUTPUT_HDF : 1
<endproperty>

<beginproperty>
NAME : downward long wave radiation
UNITS : W/m^2
DESCRIPTION : downward long wave radiation data
FILE_IN_TIME : HDF
FILENAME : ..\..\GeneralData\Atmosphere\MM5_20070606_Portugal.hdf5
DEFAULTVALUE : 0.
TIME_SERIE : 0
OUTPUT_HDF : 1
<endproperty>

<beginproperty>
NAME : upward long wave radiation
UNITS : W/m^2
DESCRIPTION : Calculated upward long wave radiation
FILE_IN_TIME : NONE
REMAIN_CONSTANT : 0
DEFAULTVALUE : 0.
TIME_SERIE : 0
OUTPUT_HDF : 1
<endproperty>

<beginproperty>
NAME : non solar flux
UNITS : W/m^2
DESCRIPTION : Calculated infrared radiation
FILE_IN_TIME : NONE
REMAIN_CONSTANT : 0
DEFAULTVALUE : 0.
TIME_SERIE : 0
OUTPUT_HDF : 1
<endproperty>

=== Atmosphere Data File ===
RUGOSITY : 0.0025
OUTPUT_TIME : 0. 86400

<beginproperty>
NAME : wind velocity X
UNITS : m/s
DESCRIPTION : wind velocity X
DEFAULTVALUE : 0.
FILE_IN_TIME : HDF
FILENAME : ..\..\GeneralData\Atmosphere\MM5_20070606_Portugal.hdf5
TIME_SERIE : 0
OUTPUT_HDF : 1
<endproperty>

<beginproperty>
NAME : wind velocity Y
UNITS : m/s
DESCRIPTION : wind velocity Y
DEFAULTVALUE : 0.
FILE_IN_TIME : HDF
FILENAME : ..\..\GeneralData\Atmosphere\MM5_20070606_Portugal.hdf5
OUTPUT_HDF : 1
<endproperty>

<beginproperty>
NAME : solar radiation
UNITS : W/m^2
DESCRIPTION : meteoIST Solar Radiation
FILE_IN_TIME : HDF
FILENAME : ..\..\GeneralData\Atmosphere\MM5_20070606_Portugal.hdf5
DEFAULTVALUE : 0.0
TIME_SERIE : 0
OUTPUT_HDF : 1
<endproperty>

<beginproperty>
NAME : air temperature
UNITS : ºC
DESCRIPTION : Temperature
DEFAULTVALUE : 0.
FILE_IN_TIME : HDF
FILENAME : ..\..\GeneralData\Atmosphere\MM5_20070606_Portugal.hdf5
TIME_SERIE : 0
OUTPUT_HDF : 1
<endproperty>

<beginproperty>
NAME : relative humidity
UNITS : fraction
DESCRIPTION : Humidity
DEFAULTVALUE : 0.
FILE_IN_TIME : HDF
FILENAME : ..\..\GeneralData\Atmosphere\MM5_20070606_Portugal.hdf5
TIME_SERIE : 0
OUTPUT_HDF : 1
<endproperty>

<beginproperty>
NAME : cloud cover
UNITS : fraction
DESCRIPTION : cloud cover from random (default)
DEFAULTVALUE : 0.
CLOUD_COVER_METHOD : 2
FILE_IN_TIME : NONE
TIME_SERIE : 0
OUTPUT_HDF : 0
<endproperty>

== Links ==

*[[Module_Atmosphere]]
*[[Module_InterfaceWaterAir]]
*[[ConvertToHDF5]]
*[[Meteo]] - Available meteorological data

[[Category:Mohid Water]]

Module InterfaceWaterAir

2008-08-18T13:11:11Z

193.136.129.1: /* Links */

== Overview ==
The water-air interface module is responsible by processes occurring at the water-air interface, such as computing [[wind surface stress|wind shear stress]], radiation balances, latent and sensible heat fluxes. This modules uses [[Module Atmosphere]] as a database for meteorological data and combines it with information from, for example, [[Module Hydrodynamic]] and [[Module WaterProperties]] to compute mass, heat and momentum fluxes across the water-air interface.

A user manual is available in the link at the bottom of the page. This user manual intends to help the user to couple atmosphere to water, activating in MOHID wind forcing, heat fluxes and mass fluxes between this interface.

== Main Processes ==

=== Momentum fluxes ===

==== Surface rugosity ====

==== Wind shear stress ====

==== Wind shear velocity ====

==== Turbulent kinetic energy ====

=== Heat fluxes ===
In MOHID heat fluxes in water column are computed with:

i) a heat source: solar radiation that enters through the water surface (surface radiation - see description) suffering a decay with depth (light extinction).

ii) a boundary condition for surface: non solar flux (see description)

iii) a boundary condition for bottom: no flux, all radiation reaching the bottom is transformed in heat

==== Short wave and long wave radiation ====
[http://en.wikipedia.org/w/index.php?title=Image:Solar_Spectrum.png&redirect=no&oldid=137135398 Solar Spectrum] at the surface is composed from ultra-violet (UV), visible and infrared (IR) bands from 250nm to 2500nm (Ohlman and Siegel 2000b). From the total solar spectrum, around 250-400nm is UV, around 400-700nm is visible and from 700-2500nm is infrared (Monteith and Unsworth, 1990).

Earth emits radiation (IR radiation) in the 3000-100000nm (or 3-100um) (Monteith and Unsworth, 1990) which means that emitted radiation has different spectra than that coming from solar origin.

Atmosphere absorbs part of emitted radiation from earth (green house gases) and emitts in the same spectrum (from 3 to 100 um)- (Monteith and Unsworth, 1990).

It is common to find the term "short wave" associated with solar radiation and "long wave" with terrestrial and atmosphere radiation because of the different well defined spectral bands.
In oceanography best care is taken to UV and visible bands because are the bands most sensible for fitoplankton and which penetrate in depth; infrared is rapidily attenuated in the first centimeters of water (Ohlman et al. 1996). As so, a "short wave solar radiation" term can be used integrating UV and visible bands and a "long wave solar radiation" for the correspondent IR band.

In MOHID it will be used the term "short wave" for UV and visible bands and longwave for IR band. This means that solar radiation has short wave (around 250-700nm) and long wave bands (around 700-2500nm) and that terrestrial (upward radiation) and atmosphere (downward radiation) are longwave bands as well (3-100um).

===== Short wave radiation =====
* Surface radiation
Surface radiation represents the solar radiation entering the water surface (after reflection - albedo).
A fraction of solar radiation is short wave radiation (60% of surface radiation by default) .

The shortwave solar spectrum represents the UV and visible bands from solar radiation (around 250 - 700nm) which are sensible for biology and penetrate in depth in the water column. The fraction of this spectra to total solar radiation is variable with gases concentration (O3, O2, water vapour, CO2) in atmosphere, solar zenith, turbidity, and mainly, by cloudiness (Ohlman and Siegel 2000a). The 60% of surface radiation used in MOHID as default for solar short wave radiation corresponds to clear sky conditions. Accordingly to Ohlman and Siegel, 2000a UV and visible spectra can undergo to 70% and 80% of total solar radiation when 40% and 90% of radiation is reduced due to clouds, respectively.

Solar radiation is an atmosphere property (see module Atmosphere for details).

===== Long wave radiation =====
* Surface radiation
Surface radiation represents the solar radiation entering the water surface (after reflection - albedo).
A fraction of solar radiation is long wave radiation (40% of surface radiation by default) .

The longwave solar spectrum represents the IR bands from solar radiation (around 700 - 2500nm) which are rapidilly attenuated in the first centimeters fo the water column. The fraction of this spectra to total solar radiation is variable with gases concentration (O3, O2, water vapour, CO2) in atmosphere, solar zenith, turbidity, and mainly, by cloudiness(Ohlman and Siegel 2000a). The 40% of surface radiation used in MOHID as default for solar long wave radiation corresponds to clear sky conditions. Adapted from Ohlman and Siegel, 2000a IR spectra from the solar radiation can undergo to 30% and 20% of total solar radiation when 40% and 90% of radiation is reduced due to clouds, respectively.

Solar radiation is an atmosphere property (see module Atmosphere for details).

* Upward long wave radiation
Heat emission from water to air related to its temperature. Represents the heat loss from water (to air) by radiation.

If computed, depends on water temperature.

* Downward long wave radiation
Heat emission from air to water related to its temperature. Represents the heat loss from air (to water) by radiation.

If computed, depends on air temperature and cloud cover.

* Net long wave radiation
Represents the balance between upward long wave radiation and downward long wave radiation.
According to Monteith and Unsworth, 1990 net long wave radiation has exit direction from earth becuase not all upward radiation is absorbed and re-emitted by green house gases.

==== Latent heat ====
Absorbed or removed heat from water when changing phase at constant temperature. In other words, is the heat that affects the physical sate of water. Represents heat exchange between water and air in terms of evaporation and condensation.

If computed, depends on water temperature, air temperature, humidity and wind velocity.

==== Sensible heat ====
Absorbed or removed heat from water due to a change in temperature. No changes in physical state occur. In other words, is the heat that affects the temperature of water. Represents the heat transfer between water and air in terms of conduction and convection.

If computed, depends on water temperature, air temperature and wind velocity.

==== Non solar flux ====
The heat flux between water and air interface that has not solar origin. Represents the balance between latent heat, sensible heat and net long wave radiation.

Non solar flux is the boundary condition at the surface for water temperature calculation.

=== Mass fluxes ===

==== Oxygen ====

==== Carbon dioxide ====

==== Surface water fluxes ====
Mass flux between the water-air interface. Represents the balance between precipitation, evaporation and irrigation.

* Evaporation
Mass flux from water to air occurring at constant temperature.
If computed, depends on latent heat, latent heat of vaporization (constant) and water density.

* Precipitation
Mass flux from rain.

* Irrigation
Mass flux from water removed by anthropogenic sources.

== User manual ==
[[Coupling Water-Atmosphere User Manual]]

== References ==
*Ohlman J.C., Siegel D.A. (2000a) - Ocean Radiant Heating. Part I: Optical Influences. Journal of Physical Oceanography, Volume 30 August 2000.
*Ohlman J.C., Siegel D.A. (2000b) - Ocean Radiant Heating. Part II: Parameterizing Solar Radiation Transmission through the Upper Ocean. Journal of Physical Oceanography, Volume 30 August 2000.
*Ohlman J.C., Siegel D.A., Gautier, C. (1996) - Ocean Mixed Layer Radiant heating and Solar Penetration: A Global Analysis. Journal of Climate, Volume 9, October 1996.
*Monteith, J.L., Unsworth, M.H. (1990) - Principles of Environmental Physics. Second Edition. Arnold Press, London. ISBN: 0 7131 2931 X

== Links ==
*[[Module_Atmosphere]]
*[[Coupling_Water-Atmosphere_User_Manual]]
*[[ConvertToHDF5]]
*[[Meteo]] - Available meteorological data

[[Category:Modules]]
[[Category:MOHID Water]]